Kirrie
Aquarium Advice Activist
Usually any "fix" medications are bad for bettas because the oils they contain can coat the betta's labyrinth organ and make it hard for them to breath. I have heard that this isn't true though. Some people have success with those medications, others have claimed that it killed their bettas. If you decide to use it, make sure you have good aeration in your tank and watch your betta so you can do a water change if he seems to have trouble breathing.
Do you have any pictures of him?
Do you have any pictures of him?